Vulcanisation accelerators for vulcanisable elastomers



United States Patent Ofi Fice Patented Oct. 10, 1961 This inventionrelates to an improved vulcanisation process; more particularly it isconcerned with novel vulcanisation accelerators.

It is an object of this invention to provide an improved class ofvulcanisation accelerators. Another object is to provide vulcanisationaccelerators which exert a powerful accelerating action at curingtemperatures. Other objects will be apparent from the description.

In accordance with the present invention it has been found that amidoderivatives of phosphoric and thiophosphoric acids which contain atleast one direct phosphor nitrogen binding are excellent vulcanisationaccelerators for natural and synthetic vulcanisable elastomers.

In a preferred form of the process of the invention, compounds of thegeneral Formula I are used as vulcanisation accelerators. In thisformula, X represents an oxygen or sulfur atom and R stands for theradical in which Y and Y each represent either hydrogen or like ordifferent, and if desired substituted, hydrocarbon radicals, or in whichY and Y together with the adjacent nitrogen atom can form a heterocyclicring system. Alkyl, cycloalkyl, aryl, and aralkyl radicals are examplesof hydrocarbon radicals; examples of heterocyclic ring systems are theethylene imino, pyrrolidino, piperidino, hexamethylene imino andmorpholino radicals.

In the formula indicated above, R and R can be like or diiferent groupseach with one of the meanings indicated under R or can if desired besubstituted alkyl, cycloalkyl, aryl or aralkyl groups, those radicalsdifferent from R either being linked directly to the phosphorus atom(P-C-bond) or linked through oxygen or sulfur atoms (P-O-C- orPS-C-bonds) to the phosphorus atom. Where R and R are bonded to thephosphorus by way of O atoms or S atoms, each of them can alternativelybe a hydrogen atom or a salt-forming cation. R and R can moreovertogether form a radical which is bonded by way of R and R twice to thesame or to different phosphorus atoms.

The following compounds are examples of the compounds to be usedaccording to the invention:

t NH @-C.

The compounds used according to the invention can be prepared by knownprocesses, for example by the process described by G. M. Kosolapoff atpage 278 et seq. in Organophosphorus Compounds (1950). The compounds canalternatively be obtained by causing ammonia to act onN-mono-substituted or N-disubstituted amidophosphoric dihalides oramidothiophosphoric acid dihalides.

The compounds in accordance with the invention are used as vulcanisationaccelerators in known manner by adding the compounds to the vulcanisableelastomer mixtures and then vulcanising the mass obtained. Generallyspeaking, good results are produced if the vulcanisation accelerators inaccordance with the invention are added in proportions of 0.05 to 5% byweight preferably 0.1 to 2% to the rubber mixtures. It is of course alsopossible to choose other proportions.

The vulcanisation accelerators in accordance with the invention canalternatively be mixed with other known vulcanisation accelerators,especially those of the mercapto-benzthiazole class, whereby anadditional activation is produced in the vulcanisation.

The vulcanisable elastomers for which the accelerators can be used aretor example natural rubber or synthetic rubber-like polymers obtained,for example, for instance from conjugated diolefines such as butadiene,dimethylbutadiene, isoprene and their homologues or copolymers ofconjugated diolefines with polymerisable vinyl compounds such asstyrene, a-methyl-styrene and their substitution products,acrylonitrile, methacrylonitrile, acrylates and methacrylates andsimilar compounds or copolymers which are obtained from iso-olefinessuch as isobu y ene a d, ts o o og es with a small amount o conjugateddiolefines. Furthermore they are suitable for polymerisates obtainedfrom chlorobutadiene and its copolymerisates obtained with monoand/ordi-olefines or other polymerisable vinyl compounds. There can be usedalso co-polymerisates of polymerisable mono-olefines with small amountsof conjugated di-olefines or polymerisates of mono-olefines whichcontain sulfochloride groups.

The following examples further illustrate the invention without, in anyway, limiting it thereto.

EXAMPLE 1 The following mixture with a natural rubber base is preparedon the roller:

Parts Crepe 50.0 Smoked shee 50.0 Zinc oxide 5.0 Stearic acid- 1.0Sulfur 2.5

1 part of N,N-dicyclohexyl phosphoric acid triamid is added to thisbasic mixture for each parts of natural rubber, and then the mixture isvulcanised in a press.

The following mixture with a base of natural rubber is prepared on the,roller:

Parts Smoked sheets 100.0 Inactive carbon black 40.0 Zinc oxide 5.0Stearic acid 1.0 Ozoken'te 1.0 Sulfur 1.5

0.7 part of dibenzthiazyl disulfide and 0.3 part of N,N-diethylphosphoric acid triamide are admixed with this basic mixture, per100 parts of natural rubber. The mixture is then vulcanised in a pressand the results thereby obtained will be seen from Table 2.

Table 2 Heating Break- Load at Tensile ing 600% Elastic- Hardstrengthelongaelongaity at ness Temp., Time, (kg/cm!) tion tion 75 0 Shore) 0.min.

By way of comparison, the values which are obtained 5 without theadditional accelerator according to the invention, but merely with theaddition of 1 part of dibenzo- 6 EXAMPLE 5 The basic mixture which isindicated in Example 2 k has added thereto 0.7 part of dibenzthiazyldisulfide and Heating Brea Load at I h Tensile mg 600% Ehstm Ham 5 0.3part of N,N ,N tr1 n butyl phosphoric acid trianude V strength elngaelongait at ness per 100 parts of natural rubber, whereupon the m x1s 2 6 25 5;? (kg/cm?) 75 Show) vulcanised in a press. The resultsobtained will be seen 5 from Table 5.

110 10 5 590 4 Table 5 5 Heating Break- Load at 143 5 75 770 38 55 31Tensile ing 500% Elastic- Hardg 3g T T itrengtl; elongaelongaity at oness O 50 186 780 99 67 41 211610., i r n e, gJcm.) tron t10n 75 CShore) thiazyl disulfide to each 100 parts of natural rubber. 110 10 5750 a 50 220 745 132 72 47 EXAMPLE 3 at a a 2 The basic mixtureindicated 1n Example 1 has admixed 10 240 770 143 70 49 therewith 0.5part of N,N-diethyl thiophosphoric acid is g8 52 Z8 Z8 triamide per 100parts of natural rubber, whereupon the 75 198 700 141 70 4s mixture isvulcanised in a press. The results obtained will be seen from Table 3.EXAMPLE 6 T bl 3 The following mixture with a base of natural rubber isprepared on the roller:

Parts Heatin Break- Load at g 'itlensile1 1ing 930% Elastiz- Hards rengte ongae ongai y a ness Tgnp 131%? (kg [cm tlon tion 75 O S ore) zlnc omde RS 5.0 Stearic acid 1.0

110 1.5 770 1 53 15 Sulfur 2.5

143 20 87 1,190 9 50 24 0.8 part of mercaptobenzthiazole and 0.2 part of$8 {$2 11 338 g 88 gg N,N,N-tricyclohexyl phosphoric acid triamide areadded so 154 945 25 59 35 to this basic mixture per 1 00 parts ofnatural rubber and then the mixture-is vulcanised in a press. The re-EXAMPLE 4 sults are shown 110 Table 6. p Table 6 The basic mixtureindicated 1n Example 1 has added I I t thereto 7 part of dibenzothiazided sulfide and 0 3 par 40 Heating Break Load at I of N,N-diethylthiophosphorlc acid triamide per 100 parts Tensile mg 60.3% Elastic.Hardof natural rubber, whereupon the mixture is vulcanised Strength e qgaelongaity t ess m a press. The results W111 be seen from Table 4. f gion 75 O Show) Table 4 110 10 870 Heatlng Break- Lo d t 143 5 144 545 7751 45 Tensile mg 600% Elastic- Hard- 1 171 625 104 70 53 strengthelongaelonga- 1ty at ness 20 159 15 10 70 54 Temp, Time, (kgJcmfl) tiontron 75 0. Shore) 40 152 25 94 9 54 0. mm. 60 145 620 83 5s 51 110 g gig$2 By way of comparison, there are indicated below the 50 273 790 107 7845 values obtained without the additional accelerator accord-- 143 ggg22 g2 g8 ing to the invention, but merely using an addition of 0.8

""" 20 225 750 93 77 44 part of mercaptobenzthiazole to 100 parts ofnatural 50 190 o 68 74 42 rubber 100 292 820 54 74 41 Heating Break-Load at 7 By way of comparison the values set out below are 11 1 1 $0070Elastic. Hard.

s rengt e ongae ongaity at ness those obtained without the additionalaccelerator accord Temp. Time (kg /cm 2) mm tion 750 Q (a Show) mg tothe invention and merely using an addition of l O m part ofdibenzothiazyl disulfide to 100 parts of natural rubber. 110 1o 730 2512 705 5 25 16 143 2 5 238 Si 33 33 H atin Break- Load at g Tensile ing600% Elastic- Hardstrength elongaelongaity at ness 40 121 655 68 59 TgnpTime, (kg/cm?) tion tlon 0 Shore) 60 112 670 62 58 5 1.5 655 EXAMPLE 720 2 s50 38 g The basic mixture which is indicated in Example 2 143 5 2850 has added thereto 0.7 part of dibenzthiazyl disulfide and g8 4 $520.3 part of N,N,N"-tricyclohexyl thiophosphoric acid 100 785 triamideper 100 parts of rubber and is then vulcanised in a press. The resultsare shown in Table 7.

Table 7 Heating Break- Load at Tensile ing 600% Elastic- Hardstrengthelongaelongaity at ness Temp, Time, (kg/cm tion tion 75 Shore) 0, min.

EXAMPLE 8 The basic mixture which is indicated in Example 2 has addedthereto 0.7 part of dibenztbiazyl disulfide and 0.3 part of cyclohexylphosphoric acid diamide per 100 parts of natural rubber and is thenvulcanised in a press. The results are shown in Table 8.

Table 8 Heating Break- Load at Tensile ing 000% Elastic- Hardstrengthelongaelongaity at ncss Temp., Time, (kg/em?) Lion tion 75 0. Shore) 0,min.

EXAMPLE 9 The following mixture with a natural rubber base is preparedon the roller:

is added to this basic mixture per 100 parts of natural rubber,whereupon the mixture is vulcanised in a press. The results are shown inTable 9.

Table 9 Heating Break- Load at Tensile ing 600% Elastic- Hardstrengthelongaelengaity at ness Temp., Time, (kg/em?) tion tion 75 0. Shore) 0.min.

8 EXAMPLE 10 The following mixture with a natural rubber base isprepared on the roller:

Parts Smoked sh 50.0 Crepe 50.0 Zinc oxi 5.0 Stearic ci 1.0 Barium sulf50.0 Sulfur 2.5

0.7 part of dibenzothiazyl disulfide and 0.3 part of phosphoric acidmonophenyl ester diamide are added to this basic mixture per parts ofnatural rubber. The mixture is then vulcanised in a press. The resultsare shown in Table 10.

Table 10 Heating Break- Load at Tensile mg 600% Elastic- Hardstrengthelongaelongaity at ness Temp Time, (kg/cm?) tion tion 75 0. Shore) 0.min.

By way of comparison, the following values are obtained without theadditional accelerator according to the invention, using only anaddition of 0.7 part of dibenzothiazyl disulfide per 100 parts ofnatural rubber.

Heating Brealr- Load at Tensile ing 600% Elastic- Hardstrengthelongaelongay at ness Temp, Time, (kg/em?) tion tion 75 0. Shore) C.min.

EXAMPLE 11 0.7 part of dibenzothiazyl disulfide and 0.3 part ofN,N-dibutyl phosphoric acid triamide are added to the basic mixtureindicated in Example 10 and per 100 parts of natural rubber, after whichthe mix is vulcanised in a press. The results are shown in Table 11.

Table 11 Heating Brcak- Load at Tensile ing 600% Elastic- Hardstrengthelongaelongaity at ness Temp, Time, (kg/pm?) tion tion 75 0. Shore) 0.min.

EXAMPLE 12 The following mixture containing a polymer of 2-chloro-1,3-butadiene is prepared on the roller:

Parts Slowly crystallising chlorobutadiene polymer.... 100.0

Zinc oxide 3.0 Light magnesium oxide 4.0 Inactive carbon black 30.0Coloring anti-ageing additive 1.0 Stearic acid-.. 3.0

0.5 part of N,N-diethyl thiophosphoric acid tn'amide is added to 100parts of elastomer and the latter is then vulcanised in a press. Theresults are shown in Table 12.

10 Instead of the N,N',N"-triphenyl thiophosphoric acid triamide therecan be used also the N,N,N"- triphenylphosphoric acid triarnide,N,N',N"-p-chlorophenyl thiophosphoric acid triamide, N,N-dirnethylamidophosphoric ble 12 Ta 5 acld-bis-p-chlorophenylester, diamido phosphoricacid phenyl ester, N-p-chlorophenyl amido phosphoric acid Heatmg E 51 fi$33 5 E.% tit Harm giethy esleir, lgl-p-tghlorophenylhdiarlnidophosphoric acid, en 11 an 1 ya ness 1 T m Time, (ii 051. iol l gio 75 0.(2 Shore) 1mm op OSP one acld p eny ester 110 g g3 gg 39 The slowlycrystallising chlorobutadiene polymer in the 50 112 5 12 41 ".1; basicmixture indicated in Example 12 is replaced by a 151 5 338 2% 2 qu1ck1ycrystalhsmg chlorobutadiene polymer and 0.5 part 20 162 730 63 50 53 ofN,N-diethyl thiophosphoric acid triamide is added to 23 1;: g? 22 2g 15the basic mixture, which is then vulcanised in apress; The

results are shown in Table 16.

EXAMPLE 13 Table 16 The basic mixture which is indicated in Example 12has added thereto 1 part of N,N-dimethyl phosphoric acid 20 HeatingBreak- Load at p tn'amide per 100 parts of elastomer, whereupon the mix3 1 ggg 283 is vulcanised in a press. The results are shown in Temn, ms/ tion tivn 5 S 7 0, mm. Table 13.

Table 13 110 5 895 37 40 64 10 121 1,125 37 47 59 Heating Break- Load at25 167 1, 120 49 54 49 Tensile 111g 600% Elastic- Hard- 50 168 905 60 5453 strength elongaelongaity at ness 151 5 177 890 50 65 49 Temp., Time,(kg/0m?) tion tion 75 0. Shore) 10 183 730 08 57 51 0. min. 20 180 71575 59 53 35 177 040 81 59 54 55 177 645 89 00 54 110 10 2 1, 485 1 25 121, 475 3 1 151 g 28 g8 2% Instead of the N,N-diethy1thiophosphonc acidtr1am1de 10 154 050 77 59 51 there can be used also the N,N-dimethylthiophosphoric 0 166 610 02 00 54 2 m 620 93 60 54 ac d tr am de or then or 1 N,N d1propyl thmphosphonc 75 171 515 94 00 54 ac1d triamide.

E PLE 14 EXAMPLE 17 The following mixture with a base of butyl rubber is0.5 part of N-methyl-N-benzylthiophosphoric acid tn- Pmpared on hroller; amide is added to the basic mixture indicated in Example Parts12 and to 100 parts of elastomer, whereupon the mixture Butyl rubber 01is vulcanised in a press. The results are shown in Zinc oxide 5 TableActive carbon black 20.0 Table 14 Spindle oil 3.0 H B k Load t Inactivecarbon bla 20.0

rea 9. ea mg Tensile;1 1111g 000% Eiastitc- Hard- Sulfur Temp" Time,E3232 6 353? 9 $33 53 555. 1 part of N,l l-diethyl thiophosphoric acidtriamide is I11111- added to this baslc mixture per 100 parts ofelastomer and the mixture is then vulcanised in a press. The results are11 10 15 1,500 4 0 25 3g fig?) 1g 41 40 shown in Table 17. 151 2 13s 9s037 44 49 Table 17 10 152 220 49 4s 51 12 51 5s a a 21 Heatin Break- Loadat 50 180 695 78 52 55 g Tensile mg 500% 11155115, 11515- strengthelongaelongain: at mess EXAMPLE 15 'Igrgp 31 3s., (kg/em.) tlon tion 75O. Shore) The basic mixture which is indicated in Example 12 has addedthereto 0.5 part of N,N,N"-tripheny1 thiophos- :3 g 5 phoric acidtriamide per 100 parts of elastomer, where- 151 go 2; 1,390 5 2s 35 uponthe mix is vulcanised in a press. The results are 2 h8g8 5,5 g? 28 shownin Table 15. 85 123 875 34 37 42 Table 15 1 120 132 370 40 40 42 B k-Load t Heating TensileJ liiig 55007;? Elastitc- Hard- EXAMPLE 18 stren te ongae onga- 1 y a ness Tem Time, (kn/051. tion tio 75 Show) Thefollowmg mixture w1th a base of chlorosulfonated polyethylene, knownunder the trade name of Hypalon,

10 21 1 340 4 was prepared on the roller: 110 25 51 1:290 8 42 36 Parts50 105 1,170 19 g 2 Hypalon 20 100.0 g ,3; gg Z; 45 2 Staybelite Resin(hydrogenated rosin) 2.5 20 1 17 840 Inactive carbon black -30.(] 23 352 50 50 lngraplast SRL (a paratfinic softener) 10.0 Litharge 40.0

11 1.5 parts of N,N-diethyl thiophosphoric acid triamide are added to100 parts of elastomer and the mixture is then vulcanised in a press.The results are shown in For comparison purpose, the following are thevalues obtained without the addition of the N,N-diethyl thiophosphoricacid triamide.

Heating Break- Load at Tensile ing 600% Elastic- Hardstrengthelongaelongaity at ness Temp, Time, (kgi/ernfl) tion tion 75 0. Shore)0. min.

EXAMPLE 19 The following mixture with a base of a co-polymer ofacrylonitrile and butadiene, with which 28% of acrylonitrile were used,is prepared on the roller:

Parts Co-polymer 100.0 Active carbon black 5.0 Zinc oxid 5.0 Plasticiser5.0 Stearic acid 1.0 Anti-ageing additive 1.5

1.0 part of N,N-diethyl thiophosphoric acid triamide and 0.5 part ofdibenzothiazyl disulfide are then added per 100.0 parts of theco-polymer and then vulcanisation is carried out in a press. The resultsare shown in Table 19.

Table 19 Heating Break- Load at Tensile ing 600% Elastic- Hardstrengthelongaelongaity at ness Temp, Time, (kg/em?) tion tion 75 0. Shore) 0.min.

For comparison purposes, the following are the values obtained withoutthe addition of N,N-diethyl thiophosphoric acid triamide, using merelyan addition of 1.5 parts of dibenzothiazyl disulfide.

Heating Break- Load at Tensile ing 600% Elastie- Hardstreugthelongae1ongaity at ness Temp, Time, (kg/emfi) tion tion C Shore) 0. min.0

111 10 8 475 7 25 s 690 8 50 11 900 9 13s 5 s 525 s 10 48 67s 10 as 1025 213 560 so 42 so 43 220 500 43 70 226 435 12s 40 71 EXAMPLE 20 15 Thefollowing mixture with a basis of cold rubber is prepared on the roller:

Parts Cold rubber 100.0 Hydrocarbon plasticiser 6.5 20 Active carbonblack 45 Active zinc oxide 5.0 Stearic acid 2.0 Paraffin 0.75Anti-ageing additive 1.5 25 Sulfur 1.8

0.42 gram of dibenzothiazyl disulfide and 0.83 gram of N,N-diethylthiophosphoric acid triamide are added per 100 parts of elastomer, andthen the mixture is vulcanised in a press, the results being shown inTable 20.

45 Instead of the N,N-diethyl thiophosphoric acid triamide there can beused also the N,N-dimethyl phosphoric acid triamide, the nori-N,N-dipropyl phosphoric acid triamide, N-cycloheXyl-N-rnethylphosphoric acid triamide, N-heptyl-N-methyl phosphoric acid triamide,morpholido- 50 phosphoric acid diamide, morpholido thiophosphoric aciddiamide, N,N-diallyl phosphoric acid diamide, N-1,2,2- trimethyIpropylphosphoric acid tn'amide, N-2,2,3,3,4,4- hexamethyl propylphosphoric acid triamide, N-Z-chloroethyl phosphoric acid triarnide or acompound of the fol- 55 lowing formulae:

1. In the process of sulfur-vulcanizing an elastomer by curing it in thepresence of 0.5-5% by weight of a vulcanization accelerator, saidelastomer being selected 75 from the group consisting of natural rubber,homopolyv 13 mers of conjugated diolefins, and copolymers of conjugateddiolefins and copolymerizable monovinyl compounds, the improvementcomprising mixing with said elastomer, a vulcanization accelerator oftheformula:

"gay R:

wherein X represents an atom selected from the group consisting ofoxygen and sulfur, Y and Y are selected from a group consisting ofhydrogen and a hydrocarbon radical containing up to 9 carbon atoms, andwherein Y and Y taken together can form with the adjacent nitrogen atoma heterocyclic ring system selected from one of the following groups:

and wherein R and R are individually selected from the group consistingof (a) wherein X represents an atom selected fromthe group consisting ofoxygen and sulfur, Y and Y are selected from the group consisting ofhydrogen and a hydrocarbon r-adical containing up to 9 carbon atoms, andwherein Y and Y taken together can form with the adjacent nitrogen atoma heterocyclic ring system selected from one of. the following groups:

and wherein R and R are individually selected from the group consistingof (a) wherein Y and Y are as defined above, and (b) a hydrocarbonradical containing up to 6 carbon atoms, a hydrocarbon oxy radicalcontaining up to 6 carbon atoms, and a hydrocarbon thia radicalcontaining up to 6 carbon atoms; said elastomer being selected from thegroup consisting of natural rubber, homopolymers of conjugateddio-lefins, and copolymers of conjugated diolefins and copolymerizablemonovinyl compounds.

3. Composition of claim 2 wherein said elastomer contains 0.12% byweight of said accelerator.

4. Process of claim 2 wherein the accelerator is N,N- dicyclohexylphosphoric acid triamide.

5. Process of claim 2 wherein the accelerator is N,N- dimethylphosphoric acid triamide.

6. Process of claim 2 wherein the accelerator is N,N- diethyl phosphoricacid triamide.

14 7. Process of claim 2 wherein the accelerator is N,N- diethylthiophosphoric acid triamide. i

8. In the process of metal vulcanizing an elastomer by curing it in thepresence of 0.55% by weight of a vulcanization accelerator, saidelastomer being selected from the group consistingor homopolymers ofconjugated chlorodiolefins, copolyrners of chlorodiolefins andcopolymerizable monovinyl compounds, and homopolymers of monoolefinswhich contain sulfochloride groups, the improvement comprising mixingwith said elastomer a vulcanization accelerator of the formula:

wherein X represents an atom selected from the group consisting ofoxygen and sulfur, Y and Y are selected from the group consisting ofhydrogen and a hydrocarbon radical containing up to 9 carbon atoms, andwherein Y and Y taken together can form with the adjacent nitrogen atoma heterocyclic ring system selected from one of the following groups:

and wherein R and R are individually selected from the group consistingof (a) wherein Y and Y are as defined above, and (b) a hydrocarbonradical containing up to 6 carbon atoms, a hydrocarbon oxy radicalcontaining up to 6 carbon atoms, and a hydrocarbon thia radicalcontaining up to 6 carbon atoms; and vulcanizing said mixture.

9. As a novel composition, an elastomer which has been vulcanized in thepresence of 0.55% by weight of a novel vulcanization accelerator, thelatter having the formula:

wherein X represents an atom selected from the group consisting ofoxygen and sulfur, Y and Y are selected from the group consisting ofhydrogen and a hydrocarbon radical containing up to 9 carbon atoms, andwherein Y and Y taken together can form with the adjacent nitrogen atoma heterocyclic ring system selected from one of the following groups:

and wherein R and R are individually selected from the group consistingof (a) wherein Y and Y are as defined above, and (b) a hydrocarbonradical containing up to 6 carbon atoms, a hydrocarbon oxy radicalcontaining up to 6 carbon atoms, and a hydrocarbon thia radicalcontaining up to 6'carbon atoms; said elastomer being selected from thegroup consisting of homopolymers of conjugated chlorodiolefins,copolymers of chlorodiolefins and copolymerizable monovinyl compounds,and homopolymers of monoolefins which contain sulfochloride groups.

10. Composition of claim 9 wherein said elastorner 14, Process of claim9 wherein the accelerator is N,N- contains 0.12% by weight of saidaccelerator. diethyl thiophosphoric acid triamide.

11. Process of claim 9 wherein the accelerator is N,N- dicyclohexylphosphoric acid triamide.

12. Process of claim 9 wherein the accelerator is 5 N,N-dimethylphosphoric acid triamide.

13. Process of claim 9 wherein the accelerator is N,N- diethylphosphoric acid triamide.

References Cited in the file of this patent UNITED STATES PATENTSRomieux et a1 July 19, 1930 Meis Feb. 12, 1935

1. IN THE PROCESS OF SULFUR-VULCANIZING AN ELASTOMER BY CURING IT IN THEPRESENCE OF 0.5-5% BY WEIGHT OF A VULCANIZATION ACCELERATOR, SAIDELASTOMER BEING SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER,HOMOPOLYMERS OF CONJUGATED DIOLEFINS, AND COPOLYMERS OF CONJUGATEDDIOLEFINS AND COPOLYMERIZABLE MONOVINYL COMPOUNDS, THE IMPROVEMENTCOMPRISING MIXING WITH SAID ELASTOMER, A VULCANIZATION ACCELERATOR OFTHE FORMULA: